The removal of sulfur-containing gases from gas streams is important in the purification of natural gas before burning it for home and industrial use and in the clean up of flue gases used in coal-burning industries. One process still widely used today employs the well known limestone scrubbing. The disadvantage of this process is the necessity of disposing of the large volume of solid waste produced. Many compounds have been suggested as absorbents, some of which are selective to H.sub.2 S or CO.sub.2. Others are capable of removing a large percent of all the acidic gases present in the gas stream being treated. One system taught in a recent patent, U.S. Pat. No. 4,366,134, employs potassium or sodium citrate to selectively remove SO.sub.2 from a gas stream. In another more recent patent, U.S. Pat. No. 4,530,704, the removal of SO.sub.2 from a gas stream is accomplished by contacting a gas stream containing it with an aqueous solution of a piperazinone, morpholinone or their N-alkyl substituted derivatives, eg N,N'-dimethyl-2-piperazinone. Each of the compounds employed by the above patents can be regenerated by the conventional method of steam stripping.
An improved method for absorbing SO.sub.2 from gas streams has now been discovered wherein hydroxyalkyl-2-piperazinones are employed as absorbents.